Recently, for reducing a greenhouse effect gas, the movement toward the use of so-called bioethanol mixed gasoline produced by mixing bioethanol which is considered neutral to carbon into gasoline has been advancing steadily. However, when ethanol is added to gasoline, gasoline is liable to absorb moisture and hence, there is a possibility that water is mixed into gasoline in a fuel tank. Further, when ethanol mixed gasoline is left for a long period, gasoline is deteriorated and an organic acid is formed in gasoline.
In this manner, when a moisture absorbed state and the deterioration of gasoline take place, ethanol can be mixed into both water and gasoline and hence, there arises a state where both water and an organic acid are contained in gasoline whereby there may be a case where a mixture of water and an organic acid is vaporized from a surface of gasoline. In such a case, there is a possibility that an inner surface of a pipe which is usually brought into contact with only gasoline vapor having substantially no corrosiveness is placed under a strong corrosive environment.
Accordingly, a pipe which is placed under an atmosphere of bioethanol mixed gasoline is required to possess corrosion resistance which is determined by taking into account also such a corrosive environment caused by fuel vapors.
Conventionally, as a material sheet for manufacturing a fuel pipe for an automobile, a cold-rolled steel sheet without further treatment or a copper plated steel sheet has been popularly used. Further, a pipe which is manufactured using a stainless steel sheet as a material sheet and a pipe to which Sn—Zn plating is applied have been proposed.
For example, patent literature 1 describes a galvanized steel sheet for a fuel container aiming at the enhancement of durability of an inner surface of the fuel container against fuel, the enhancement of corrosion resistance of an outer surface after coating and the like, wherein the galvanized steel sheet is manufactured such that a post-treatment film is applied to a surface of a galvanized steel sheet by 0.1 to 2.0 g/m2 as a coating weight, and then the galvanized steel sheet is dried by controlling a drying condition of the post-treatment film where a temperature of the galvanized steel sheet is elevated by heating from a plated surface side at a heating rate of 20° C./s or more to dry the post-treatment film.